<p>In this study, high-magnesium Al-8Mg-0.6Mn alloys with various Zn contents (0~4 wt%) were prepared via gravity casting using a metal mold, and the influences of Zn on the microstructure and mechanical properties of the as-cast alloys were investigated. The alloy without Zn is predominantly composed of α-Al, Al₆(Fe, Mn) and β-Al₃Mg₂ phases. The addition of Zn markedly enhances the formation of the T-Mg₃₂(Al, Zn)₄₉ phase, which progressively substitutes the β-Al₃Mg₂ phase, thereby forming a multiphase structure consisting of α-Al, Al₆(Fe, Mn), and primary and eutectic T phases. The grain size was refined, and the phase stability was enhanced. Regarding mechanical properties, when the Zn content rose from 0 to 4 wt%, the tensile strength of the alloy increased from 199 to 245 MPa, the yield strength increased from 131 to 232 MPa, and the hardness increased from 97 to 118 HV. However, the elongation decreased from 6.8 to 2.2%, and the plasticity decreased significantly. The fracture mechanism transformed from ductile to brittle, and the high-Zn alloy exhibited quasi-cleavage fracture characteristics. This study discloses the influence of Zn on the microstructure and mechanical properties of Al-Mg-Mn alloys, providing a theoretical basis for the development of high-performance cast aluminum alloys.</p>